1. 2.5 Investigating Ecosystems Practical Work
Environmental Systems & Societies

2. Significant Ideas
The description and investigation of ecosystems allows for comparisons to be made between different ecosystems and for them to be monitored, modelled and evaluated over time, measuring both natural changes and human impacts.
Ecosystems can be better understood through the investigation and quantification of their components.

3. Knowledge & Understandings
The study of an ecosystem requires that it be named and located ex: Sundarban’s, Bangladesh, a Mangrove forest along the South-western coastline of Bangladesh
Organisms in named and located an ecosystem can be identified using a variety of tools including dichotomous keys, comparisons to herbarium/ specimen collections, technologies and scientific expertise.
Sampling strategies may be used to measure biotic and abiotic factors and their change in space, along an environmental gradient, over time, through succession or before and after a human impact, for example as part of an EIA.
Measurements should be repeated to increase reliability of data. The number of repetitions required depends on the factor being measured.
Methods for estimating the biomass and energy of trophic levels in a community include measurement of dry mass, controlled combustion, and extrapolation from samples. Data from these methods can be used to construct ecological pyramids.

4. Knowledge & Understandings
Methods for estimating the abundance of non-motile organisms include the use of quadrats for making actual counts, measuring population density, percentage coverage, and percentage frequency.
Direct and indirect methods for estimating the abundance of motile organisms can be described and evaluated. Direct methods include actual counts and sampling. Indirect methods include the use of capture- mark-recapture with the application of the Lincoln Index.
Species richness is the number of species in a community and is a useful comparative measure.
Species diversity is a function of the number of species and their relative abundance and can be compared using an index. There are many versions of diversity indices but students are only expected to be able to apply and evaluate the results of the Simpson Diversity Index. Using its formula, the higher the result, the greater the species diversity. This indication of diversity is only useful when comparing two similar habitats or the same habitat over time.

5. Application & Skills Design and carry out ecological investigations.
Construct simple identification keys for up to eight species.
Evaluate sampling strategies.
Evaluate methods to measure at least three abiotic factors in an ecosystem.
Evaluate methods to investigate the change along an environmental gradient and the effect of a human impact in an ecosystem.
Evaluate methods for estimating biomass at different trophic levels in an ecosystem.
Evaluate methods for measuring/estimating populations of motile and non-motile organisms.
Calculate and interpret data for species richness and diversity
Draw graphs to illustrate species diversity in a community over time or between communities.

6. IB Animal Experimentation Policy
You may not perform an experimentation using animals that involves:
Pain, undue stress, damage to health of animal
Death of animal
Drug intake or dietary change beyond those easily tolerated by the animal
Consider:
Using cells, plants or simulations instead
If using humans you MUST have written permission
AISD safety contracts apply at ALL times during ALL labs
No experiments may be done that have any risk of transferring blood-borne pathogens

7. K2: Dichotomous Keys Method of identifying an organism
Dichotomous = divided in two parts
Numbered series of pairs of descriptors
One matches the species, the other is clearly wrong
Each pair leads to another pair of descriptors OR to an identification
Features chosen for descriptors should be easily visible and observable

8. K2: Dichotomous Keys

9. K2: Practice Salamander Keying Shark Keying
Look at identification book examples and large dichotomous keys on the front table

10. A2: Creating Dichotomous Keys
As a group, create a dichotomous key for your bag of hardware store items.
REMEMBER:
There are always only 2 choices (1a or 1b)
You may start with a branching diagram but this must be turned into a outline form for final draft
It is easiest to start by grouping all objects into 2 groups, then take one group and divide into 2 again until you get to individual items.
Traits should be used that ANYONE would be able to observe and come to the same conclusion
When naming your organisms they should have a Genus species name

11. A2: HOMEWORK
Complete your own dichotomous key of the creatures (sent by )
me a copy of your dichotomous key and make an answer key on the second page.
Your key will be assessed by your peers, we will exchange keys and see if they work.

12. COLLECTING DATA - Where?
When collecting environmental data, it is almost impossible to collect every possible data point
We use sampling methods to make estimations
These methods enable us to get a random sample from an entire ecosystem and then use extrapolation to make estimates and predictions
In order to avoid bias it is important that these methods are truly random.
Two methods used in ecology to determine where to collect a sample are quadrats and transects.

13. Assumptions Made When Sampling
The sample is representative of the whole system
It is necessary to take enough samples so that an accurate representation is obtained
It is important to avoid bias when sampling

14. Common Sampling Methods
Abundance of Non-motile Organisms
Transects and Quadrants
Abundance of Motile Organism
Actual Count (very difficult if large system)
Lincoln Index
Capture – Mark - Recapture
Species Diversity
Simpson Diversity Index
For comparing 2 habitats or the change in one habitat over time

15. TRANSECTS Samples taken at fixed intervals
Set up along an environmental gradient (e.g. high to low on a mountain, from shoreline)

16. Line Transects
A measured line is randomly placed across the area in the direction of an environmental gradient
All species touching the line are recorded along the whole length of the line or at specific points along the line
Measures presence or absence of species

17. Belt Transects
Transect line is laid out and a quadrant is placed at each survey interval
Samples are identified and abundance is estimated
Slow moving animals (limpets, barnacles, snails) are collected, identified then released
For plants an percent coverage is estimated
Data collection should be completed by one individual as estimates can vary person to person

18. Quadrats Species Distribution: Population Density
Measuring Non-motile Organisms
Square Quadrat – for population density
Size of quadrat determined by size of organism being sampled
(10 x 10 cm = 0.01 m2; 0.5 x 0.5m = 0.25 m2, 1.0 x1.0 m = 1 m2 or 5.0 x5.0 m = 25 m2)
Count all individuals within a randomly placed quadrat
Population density is expressed as number of individuals per square meter
The larger the size and larger the sample the more accurate the results
Quadrats Species Distribution: Population Density

19. SQUARE QUADRAT Find the population density
10 cm
Find the population density
Determine the size of the quadrat (in m2)
10 cm x 10 cm = 100 cm2 = 0.01 m2
Count all individuals IN quadrat 22
Calculate population density number of individuals per square meter
22 𝑓𝑙𝑜𝑤𝑒𝑟𝑠 𝑚 2 =2200 𝑓𝑙𝑜𝑤𝑒𝑟𝑠 𝑝𝑒𝑟 𝑠𝑞. 𝑚.
10 cm

20. Grid Quadrat Grid Quadrat
Measures percent frequency – the % of quadrats in which the species is found OR
Measures percent coverage –the % of area within a quadrat covered by a single species
NOTE: When you are looking at one species at a time
If not using a 10 x 10, you must turn into a percentage (squares covered/total # of squares)

21. Percent Frequency Find the percent frequency
Count number of squares with flowers
15 (note one square has 2 flowers)
Count total number of squares 36
Calculate percentage
15 36 ×100=42%

22. http://www. slideshare

23. Percent Coverage Find the percent coverage Count full squares
Now combine pieces to make full squares
Calculate percentage coverage
1 m 18 14 22 24 24 1 2 14 15 3 4 15
1 m 17 21 23 12 19 20
%= 𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑡𝑜𝑡𝑎𝑙 𝑠𝑞𝑢𝑎𝑟𝑒𝑠 ×100
= ×100=24% 13 13 17 18 5 6 12 16 7 8 9 10 11 22 19 23 20 16 12 21

24. How choose quadrat size?
Think about the size of the organism.
Think about the area of the system.
The smaller the quadrat the more accurate, however the smaller the sample size
Larger quadrats increase inaccuracy but allow for broader sample of an area

25. How many samples?
Obviously the more samples you collect, the more accurate your estimates for the entire ecosystem.
Generally collect enough quadrats that the number of species collected levels out

26. Time to Practice Using Quadrats in Lab find the:
Population Density
Percent Frequency
Percent Coverage
Estimating Percentage Coverage with Quadrats Wkst
Random Sampling Lab

27. Measuring Biomass
Get a sample of the organisms, dry them out completely in a dehydrating oven (to remove all water!), find the mass and extrapolate :
If you collect 10 plants, dry them out and find their average dry biomass to be 20g, what would the biomass of a population of plants be?
50,000g
Remember – biomass can be used to create pyramids of biomass when looking at energy transfers and is needed for many productivity calculations!

28. Measuring abundance of Mobile Organisms
If the organism is mobile we use a method called the capture-mark-recapture method
We then use this data to calculate the Lincoln Index
𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥= 𝑛 1 × 𝑛 2 𝑛 𝑚
𝑛 1 =𝑛𝑢𝑚𝑏𝑒𝑟 𝑐𝑎𝑢𝑔ℎ𝑡 𝑓𝑖𝑟𝑠𝑡 𝑠𝑎𝑚𝑝𝑙𝑒
𝑛 2 =𝑛𝑢𝑚𝑏𝑒𝑟 𝑐𝑎𝑢𝑔ℎ𝑡 𝑠𝑒𝑐𝑜𝑛𝑑 𝑠𝑎𝑚𝑝𝑙𝑒
𝑛 𝑚 =𝑛𝑢𝑚𝑏𝑒𝑟 𝑚𝑎𝑟𝑘𝑒𝑑 𝑜𝑛 𝑠𝑒𝑐𝑜𝑛𝑑 𝑠𝑎𝑚𝑝𝑙𝑒

29. How to Capture Motile Organisms
REMEMBER: IB Animal Experimentation Policy
Pitfall Traps
Small Mammal Traps
Tullgren Funnels (invertebrates)
Kick Net

30. Capture – Mark – Recapture
Capture organisms and count
Mark organisms with non-toxic, semi- permanent, substance that will not increase the likelihood of harm to the organism
Release organism back into environment
The time before you do another capture will depend on; the mobility of the organism, r or K strategists

31. Assumptions
The population of organisms must be closed, no immigration or emigration.
The time between samples must be small compared to the life span of the organism
The marked organisms must mix completely with the rest of the population during the time between sampling.

32. Using Lincoln Index
In a woodland, the undergrowth was sampled for snails and 430 were found and marked. They were then released and the population similarly sampled after a two-week period. This second sampling produced 410 snails, 100 of which were marked.

33. n1 = 430
n2 = 410
m2 = 100
N = 430 x 410 = 1763 snails
100

34. Using Lincoln Index
While studying field voles, an ecologist caught 500 and ringed a foot of each before releasing them. Every day for the next two weeks he examined the waste material found in the nests of their predators. He collected a total of 300 field vole skulls and 15 rings.
How many field voles were
probably in the area examined?

35. N = 300 x 500 = 10,000 15

36. Your Turn
Use the Lincoln Index to monitor this mountain gorilla population over time:
Year
2003
2004
2005
2006
2007
2008 n1 23 26 27 16 18 17 n2 25 30 35 19 24 nm 22 21 15 P
Gorilla hunting is illegal in some regions and carefully controlled in others, though there is a high demand for illegal bush-meat.
Deduce between which two years illegal hunters were active in the forest.
Explain the long recovery time for the population.

37. Some Possible Sources of Error with Capture – Mark – Recapture
Emigration & Immigration
Natural disaster or disturbance between captures
Trap happy or trap shy individuals
Organisms did not have enough time to disperse back into ecosystem
Animals lost marks between recapture

38. LAB: Capture-Mark-Recapture & Lincoln Index (Beans & Rice)

39. Species Diversity
The two main factors taken into account when measuring species diversity
1. Richness
A measure of the number of different species present in a particular area.
The more species present in a sample, the 'richer' the sample.
Takes no account of the number of individuals of each species present. It gives as much weight to those species which have very few individuals as to those which have many individuals.
2. Relative Abundance
The relative number of individuals of each species present

40. Simpson’s Diversity Index
D= N(N-1)
∑n(n-1)
D = diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
You are not required to memorize this formula but must know the meaning of the symbols.

41. Analyzing Simpson’s Index
Used to compare 2 different ecosystems or to monitor an ecosystem over time
D values have no units and are used as comparison to each other
High D Value Indicates:
Stable and ancient site
More diversity
Healthy habitat
Low D Value Indicates:
Dominance by one species
Environmental stress
Pollution, colonization, agriculture

42. Using Simpson’s Index:
Numbers of individuals (n)
Flower Species
Sample 1
Sample 2
Daisy
300 20
Dandelion
335 49
Buttercup
365
931
Total (N)
1000
Find the diversity index for sample 1:
𝐷= 𝑁(𝑁−1) 𝑛(𝑛−1)
𝐷= 1000(999) 300∙ ∙334 +(365∙364)
𝐷=2.99

43. Using Simpson’s Index:
Numbers of individuals (n)
Flower Species
Sample 1
Sample 2
Daisy
300 20
Dandelion
335 49
Buttercup
365
931
Total (N)
1000
Now, find the diversity index for sample 2:
𝐷= 𝑁(𝑁−1) 𝑛(𝑛−1)
𝐷= 1000(999) 20∙ ∙48 +(931∙930)
𝐷=1.15

44. Sample 1 has a higher Simpson’s Biodiversity index than Sample 2 even though it has the same number of species present and the same number of total individuals because there is more even distribution of the organisms through the species.

45. YOUR TURN
The insects in two meadows are being investigated. The following data was collected. Compare the diversity of the two meadows
Organism
Description
Meadow 1
Meadow 2
Orthoptera (grasshopper)
Green with red legs 16 25
Brown with yellow stripe. 5 2
Lepidoptera (butterfly)
Large, blue 26 17
Small, blue 3 9
Coleoptera (beetle)
Red & Blue 12
Hymenoptera (wasp)
Black
Purple 4
Hymenoptera (bee)
Striped

46. YOUR TURN Solution
Organism
Description
Meadow 1
Meadow 2
Orthoptera (grasshopper)
Green with red legs 16 25
Brown with yellow stripe. 5 2
Lepidoptera (butterfly)
Large, blue 26 17
Small, blue 3 9
Coleoptera (beetle)
Red & Blue 12
Hymenoptera (wasp)
Black
Purple 4
Hymenoptera (bee)
Striped
𝐷 1 = 62(61) 16∙15 + 5∙4 + 26∙25 + 3∙2 +(12∙11) = =3.6
𝐷 2 = 74(73) 25∙24 + 2∙1 + 17∙16 + 9∙8 + 12∙11 + 4∙3 +(5∙4)
= =4.9

47. Lab activity with playing cards Simpson’s Diversity Homework Questions
Simpson’s Index
Lab activity with playing cards
Simpson’s Diversity Homework Questions